Variable neutralizing condenser



Feb. 22,1927. 1,618,255

4 VJ. J. WOOD VARIABLE NEUTRALIZING CONDENSER Filed May16 1925 I N VEN TOR.

asta Feb. 22,1927.

JOHN J. wool), ornnnvnn coLoiiAno.

VARIA LE NEUTRALIZING ooivnnifiismt.

Application filed May 16', 1925. Serial No. 30,814.

ratus to automatically at any position of thetuning condenser; transfer around the audion 7, tube tobe neutralizech' the correct famountof energy fromthe plate circuit to 1 0 'thegrid circuit to exactly counteract the .tfed back? current, within the audion tube, 7- as 'we'll'a'sany external currents that might induce oscillations within the tube.

variable neutralizing condenser is applicableto most radio frequency amplifying circu ts that employ condensers for tuning. ltiinp'a'rt's'toi any circuit in which it is used the stable characteristics that follow the use p of fixed 'neut'ra'lizers, Without the heavy -2Q 1osses which the use of these latter entail.

Its iisje'eiiables the operation of the an ditin'tube at its most 'eiiicient point at'all tiin'csg jwithout, the exercise of'eiiort or skill onthepart of the operator. I f

understood that my invention covers structural-variations from this specification yvhi'chiaife desirable to adopt it to: any

' ing apparatus.

'i'The ap o fre quency amplifying cir 1 7 ed in Fig. 1 of the drawings. view sfshowing the construction and which Ifprjer r to use are shown Fg 2 whic'h de'pict's a longitudinal sech automatic neutralizing c onerm untied an a standard tuning con cui is ill-ustrat 'den tratin'g the arrangement and extent of the plates.

.In the circuit diagram, Fig. 1, the audion tube to be neutralized is indicated at a, the tuning condenser at 6, and my variable neutralizing condenser at 0. Its position, connection and operation inthe circuit are ex- ,actly similar to other neutralizing condensers now: in use and form no part of my invention, so that a detail description of these 501 is unnecessary to its comprehension.

In the detail drawings, Figs. 2 and 3, the I tuning condenser I) is mounted in the usual Qmanner, upon a panel 1, its shaft 2cextending through the panel and having an operating knob- 3 aflixedto its outer end.

" Operat-ivelyattached to the inner or option ofmyinvention to a comd foperatedffrom the same control; 1 and 1'1 1 F1g. 3 which shows an end view of my automatic, neutralizing condenser. 1llusposite end of shaft 2 by means of a set screw 4 1s a couphng 5, which is also pinned or otherwise fastened to shaft 6 oiiny automatic neutralizing condenser c. 1 Shaft 6 pros jects through a boss formed in the center of a supporting plate 7, of dielectric material. Supporting plate is mounted on an extension 8 of one of the supporting studs of tuning condenser b .and serves to support and electrically insulate the parts of my automatic neutralizing condenser c and to maintain the alignment of shafts 2 and 6.

The stationary plates of my variable nen' tralizing condenser consist of two parallel sectors 9 and 9. Soldered or otherwise atfixed to plates 9 and 9 are bosses 10 and 10 respectively; adapted for screw threaded engagement with adjusting screw 11. That portion of adjusting screw 11 which is traversed by boss 10 is threaded in a left hand direction. while "the portion traversed by boss 10 is threaded in a right hand direction, or vice versa. An operating knob'll is pressed onto an extension of adjusting screw 11 and it will be clear from the foregoing that rotation of knob 11 and adjusting screw 11' in one'direction will draw bosses 10 and '10, together with plates 9 and9 toward each other,' while the reverse rotation will "move them away from. each other. I

Adjusting screw 11" is hollow and loosely fittedfover mounting screw 12 which is threaded into supportingplate 7 thus permitting free rotationof adjusting screw 11 without en'dwise movemen In order to preserve their correct alignment and insure that. they will move only in a linear direction plates.9 -an'd 9are perforated and adapted to slide freely over guiding studs 13 and 13, which are fastened into supporting plate 7.

The movable plate of my variable neutralizing condenser is formed of two or more sectors, 14 and 1e, clamped against .a shoulder on shaft 6 by means of a nut 15. By looseningnut 15 these sectors can be spread fanwise to form a large sector, or contracted to form a small one, for the purpose fully explained hereinafter.

- Either the plate or the grid side of audion tube a is electrically connected to stationary plates through a binding post 16 formed on mounting screw 12. The opposite side of audion tube a is electrically connected to the movable plate 14 and 14:

A point exists in the range of signal fre quencies at which oscillations will be induced in audion tube a, in any particular receiving set. This point is probably not the same in any two sets and may even vary with different tubes. Until this point is reached,

1 no neutralizing device is necessary and its use introduces needless losses into the circuit.

By means of set screw 4 in coupling 5 between shaft 2 of the tuning condenser and shaft 6 of my variable neutralizing condenser movable plate 14 and 14' of the latter may be adjusted to enter the active space between stationary plates 9 and 9 at exactly the frequency thatits use becomes necessary.

The range of frequencies through which a neutralizing condenser is necessary also varies with different sets, as does the neces sary intensity of neutralizing action at particular frequencies. The spreading or contracting of sectors 14 and 14: composing the movable plate, facilitate the adjustment of my automatic neutralizing condenser to exactly co-operate with'the individual audion tube to be neutralized, both in duration and intensity of its action. 7

The maximum intensity of necessary neutralizing action is also variable. The maximumcapacity of my variable neutralizing condenser may be easily and accurately regu lated by moving stationary plates 9 and 9' by means of adjusting screw 11. Turning this screw in a direction to decrease the distance between stationary plates 9 and 9 and movable plates l iand 1 L, increases the maximum capacity of the condenser. Reverse.

movement of adjusting screw 11 has the opposite effect. c

From the foregoing it will be clear that my invention provides a variable neutralizing condenser having a sufficient range of adjustments to adapt it to many receiving sets, and that when once adjusted to the individual apparatus its action will thereafter be entirely automatic, requiring no effort nor attention on the part of the operator.

Having thus described my invention, I claim and desire to secure by Letters Patent of the United States, the following:

1. A variable neutralizing condenser, adapted to be operated in conjunction with a tuning condenser, comprising one or more stationary plates, supporting means, electrical connections, an operating shaft, a coupling operatively connecting said operating shaft with the operating means of said tuning condenser, and one or more movable plates adjustably afiixed to said operating shaft, each of said plates comprising a series of parallel sectors adapted to be spread fanwise to any desired extent or contacted to the width of a single sector 7 2. A variable neutralizing condenser, adapted to be operated in conjunction with a tuning condenser, comprising an operating shaft, a coupling between said opera-ting shaft and the operating shaft of said tunin condenser, one or more movable plates 11 justably ailixed to said operating shaft, supporting means and electrical connections, together with one or more stationary plates and means operable to vary the s aces between said movable plates and sai stationary plates.

3. A variable neutralizing condenser, adapted to be operated in conjunction with a. tuning condenser and comprising an operating shaft, one or more movable plates adjustably affixed to said operating shaft, one or more stationary plates ad ustably spaced from said movable plates, and means for adjustably coupling said operating shaft with the operating shaft of said tunin cone denser, said adjustable coupling means eing operable to permit alteration of the angular] position of the shaft of said variable neutralizlng condenser with respect to the 'operating shaft of said tuning condenser.

JOHN J. WOOD. 

